Manufacturing disk drives is a very competitive business. People that buy disk drives are demanding disk drives that are capable of storing data at ever higher densities. A magnetic head is used to read data from a disk and to write data to a disk. A slider is typically used to position the magnetic head over the appropriate location on a disk.
The density that data can be stored on and read from a disk is directly proportional to the height that the slider's air bearing surface flies over the disk (also commonly known as “fly height”). For example, the closer that the slider can fly over a disk the more data that can be stored and read from the disk. However, the probability that a slider will come into contact with a disk increases as the fly height decreases. Contact between the slider and the disk can result in permanent damage to the disk.